ABSTRACT
Mapping sequences onto biopolymer structures is characterized by redundancy since the number of sequences exceeds the number of structures. The degree of redundancy depends on the notion of structure. The chapter considers two classes of biopolymers, RNA molecules and proteins. In the precise view of X-ray crystallography of biopolymers, sequence redundancy is nonexistent: Small as they may be there are always differences in atomic coordinates that make structures unique. Mapping RNA genotypes onto phenotypes becomes accessible to straightforward analysis when the phenotype can be identified with the molecular structure of the RNA molecules. Mapping RNA genotypes into phenotypes requires a solution to the structure prediction problem. Genotype-phenotype mappings of RNA molecules have been investigated using a prediction algorithm for secondary structures and by means of inverse folding. RNA secondary structures and protein folds are highly redundant in the sense that many sequences fold into the same shape.
